﻿using System;
using Velocity4Net.Ctx;
using Velocity4Net.Util.Introspection;

namespace Velocity4Net.App.Event
{

    /*
     * Licensed to the Apache Software Foundation (ASF) under one
     * or more contributor license agreements.  See the NOTICE file
     * distributed with this work for additional information
     * regarding copyright ownership.  The ASF licenses this file
     * to you under the Apache License, Version 2.0 (the
     * "License"); you may not use this file except in compliance
     * with the License.  You may obtain a copy of the License at
     *
     *   http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing,
     * software distributed under the License is distributed on an
     * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
     * KIND, either express or implied.  See the License for the
     * specific language governing permissions and limitations
     * under the License.
     */




    /**
     * Event handler called when an invalid reference is encountered.  Allows
     * the application to report errors or substitute return values. May be chained
     * in sequence; the behavior will differ per method.
     *
     * <p>This feature should be regarded as experimental.
     *
     * @author <a href="mailto:wglass@forio.com">Will Glass-Husain</a>
     * @version $Id: InvalidReferenceEventHandler.java 1780734 2017-01-28 19:21:08Z cbrisson $
     * @since 1.5
     */
    public interface InvalidReferenceEventHandler : EventHandler
    {

        /**
         * Called when object is null or there is no getter for the given
         * property.  Also called for invalid references without properties.
         * invalidGetMethod() will be called in sequence for
         * each link in the chain until the first non-null value is
         * returned.
         *
         * @param context the context when the reference was found invalid
         * @param reference string with complete invalid reference
         * @param object the object referred to, or null if not found
         * @param property the property name from the reference
         * @param info contains template, line, column details
         * @return substitute return value for missing reference, or null if no substitute
         */
        Object invalidGetMethod(Context context, String reference,
                                Object _object, String property, Info info);

        /**
         * Called when object is null or there is no setter for the given
         * property.  invalidSetMethod() will be called in sequence for
         * each link in the chain until a true value is returned.  It's
         * recommended that false be returned as a default to allow
         * for easy chaining.
         *
         * @param context the context when the reference was found invalid
         * @param leftreference left reference being assigned to
         * @param rightreference invalid reference on the right
         * @param info contains info on template, line, col
         *
         * @return if true then stop calling invalidSetMethod along the
         * chain.
         */
        bool invalidSetMethod(Context context, String leftreference,
                                 String rightreference, Info info);

        /**
         * Called when object is null or the given method does not exist.
         * invalidMethod() will be called in sequence for each link in
         * the chain until the first non-null value is returned.
         *
         * @param context the context when the reference was found invalid
         * @param reference string with complete invalid reference
         * @param object the object referred to, or null if not found
         * @param method the name of the (non-existent) method
         * @param info contains template, line, column details
         * @return substitute return value for missing reference, or null if no substitute
         */
        Object invalidMethod(Context context, String reference,
                             Object _object, String method, Info info);
    }
}